The progression of the human genome project has led to a wide recognition of the importance of developing gene maps of homologous genes in other mammal species, both as an index for comparative evolutionary analysis as well as for a resource for gene mapping in model organisms. To date, there are approximately 25 mammal species with gene maps representing 8 of 19 mammalian orders. The Genetics Section has contributed to the effort by concentrating in the past on constructing a gene map of the domestic cat, Felis catus. The framework map has been developed using a panel of rodent x cat somatic cell hybrids and in situ hybridization to metaphase chromosomes. A representative map of over 100 Type I gene coding loci have been assigned to chromosomes. To expand this map, we have designated 321 anchored reference loci for comparative gene mapping and initiated interspecies linkage crosses between F. catus and Prionailurus bengalensis, the Asian leopard cat. To date, over 80 interspecies hybrid offspring have been born following artificial insemination; of these, 12 healthy females are maturing. Methods for in situ hybridization of feline metaphase chromosomes using biotin-labeled molecular clones have been attempted and improved. Procedures using human chromosome libraries for chromosome "painting," i.e., visualization of homologous chromosome segments between carnivores and primates, are in progress.